According to Galveston police, the father's attempt to rescue his 5-year-old child took place after 7 p.m. on the north side of the bridge at the pass.
The boy went into the water amid treacherous swimming conditions, police said. With the boy in distress, the father went in to rescue the child but went under water.
The father did not survive, according to police. The boy was pulled out and taken to a nearby hospital. The child's condition was not immediately disclosed.
Galveston County officials identified the dad as 27-year-old Rufino Suarez. They said Suarez was found in almost the exact location where he went under.
San Luis Pass has been noted for conditions unfriendly to swimmers. Last month, a 19-year-old fisherman went missing at the pass. His body was later found.
Earlier this week, Galveston Island Beach Patrol issued a red flag warning due to the potential for strong rip currents. The patrol singled out San Luis Pass as an area to avoid.
WATCH: How to survive a rip current
VIDEO: Survive a Rip Current